JPH01107340A - Production of optical disk - Google Patents

Abstract

PURPOSE:To improve the adhesiveness between a plastic substrate and film by reforming the surface of the substrate by using energy particles. CONSTITUTION:The surface of the plastic substrate is reformed to form many strong bonds between the substrate and the film formed on the surface thereof. Namely, surface energy decreases and the points (active points) bonding to the film material formed on the surface increase when the surface is subjected to plasma irradiation. The mixed layer of the substrate material and the film material exists at the boundary face between the substrate and the film formed on the surface thereof and the distinct boundaries are no longer visible when the surface is subjected to the irradiation of a neutral ion beam. Namely, the mixture layer 2 exists between an underlying film 3 deposited on the surface and the substrate 1 and the distinct boundaries do not exist therebetween if silicon nitride which is the material for the underlying film 3 is implanted into the substrate 1 by using an ion mixing device of an ion mixing method and if the film is formed simultaneously therewith. The adhesiveness between the substrate 1 and the film formed on the surface thereof is thereby improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a disc that performs recording, reproduction, and erasing using laser light, and particularly relates to a method for manufacturing a disc that uses laser light to perform recording, reproduction, and erasing.
The present invention relates to a method of manufacturing an optical disc suitable for achieving high reliability.

[Conventional technology]

With the development of an advanced information society, the need for high-density, large-capacity file memory is increasing. Among these, optical discs that use laser light for recording and playback are attracting attention as a memory that can meet these needs. Optical disks can be roughly divided into two types: write-once disks, which allow recording only once, and magneto-optical disks and phase-change disks, which are rewritable.
It is classified as

A glass substrate with guide grooves formed on the surface by a photopolymer method (2P method) is used for the substrate of these disks. However, in consideration of future mass production of disks, it is desired to use plastic substrates that can be mass-produced by techniques such as injection molding or integral molding.

One of the problems when using these substrates is that the adhesion between the substrate and the film formed thereon is poor. As a known example of dealing with this problem, Japanese Patent Laid-Open No. 60-2010 discloses forming a recording film in an atmosphere containing a reducing gas.
No. 43843.

[Problem that the invention seeks to solve]

In the conventional technology described above, when a film is formed on a plastic substrate, the bond formed between the substrate and the film is weak, and if left in a high temperature and high humidity environment, problems such as peeling of the film and cracks in the film occur. was there.

The object of the present invention is to improve the adhesion between the substrate and the film.

It is an object of the present invention to provide a method for manufacturing an optical disc having high reliability and long life.

[Means for solving problems]

The above object is achieved by modifying the surface of a plastic substrate using energetic particles to lower the surface energy.

More specifically, this is achieved by irradiating plasma of an inert gas that does not react with the substrate material or an inert gas containing a reactive gas, or by ion implantation or ion mixing.

[Effect]

By modifying the surface of the plastic substrate.

By forming many strong bonds between the substrate and the film formed on its surface, the adhesive strength between the substrate and the film can be increased. That is, when plasma irradiation is performed, the single surface energy decreases, and the number of points (active points) that bond with the film material formed on the surface increases, and the adhesion between the substrate and the film becomes stronger.

Furthermore, when irradiation with a neutral ion beam is performed, a mixed layer of the substrate material and the film material exists at the interface between the substrate and the film formed on its surface, and no clear boundary can be seen. As a result, the adhesion between the substrate and the film is dramatically increased.

〔Example〕

The details of the present invention will be explained below using Examples 4 to 4. [Example 1] In this example, a mixture layer of a substrate material and a film material is formed at the interface between a plastic substrate and a film formed thereon. This is the case when . Figure 1 shows a schematic diagram of the cross-sectional structure of the manufactured optical disk. On a resin substrate or a substrate 1 having a resin layer on the surface, silicon nitride as a base film material is implanted into the substrate 1 by the ion mixing method, and at the same time the surface A membrane of 800 people was formed.

The outline of the ion mixing device used here is shown in Figure 2.A mixture layer 2 exists between the base film 3 deposited on the surface and the substrate 1, and Dep.
When the th-profile was measured, there was no clear boundary, but a mixed layer of both. By the way, if the mixed layer 2 is too thick, it will become an obstacle to the passage of light, and if it is too thin, the effect of improving adhesion will be small, so there naturally exists an appropriate value. The thickness depends on the material of the substrate used or the material of the underlying film. After forming this base film, a TbFeCoNb information film 4 was subsequently formed using a sputtering method. As a sputter target.

An alloy having the composition Tbza, oFaeo, 3Cot2Nha, a was used, and Ar was used as the discharge gas. The conditions for sputtering are: input RFt force density: 4.
5W/cd, discharge voltage crab 5 X 10-s (Torr
), substrate rotation speed: 2 Orpm. This film is a magneto-optical recording film and has the following magnetic properties. Kerr rotation angle = θ = 0.30', coercive crab Hc = 8 K
Oe, Curie temperature: Ta=200°C. This information recording film can also be a phase change type recording film limited to magneto-optical recording.
A write-once recording film may be used, and finally a silicon nitride protective film 5 was formed by sputtering. A 5iaNa sintered body was used as a target, and an Ar-NZ mixed gas (
Nz/Ar=20/80) were used, respectively. Then, the discharge gas pressure was set to 2×10-”To as sputtering conditions.
The RF power density and substrate rotation speed were the same as in the case of the previous recording film except that rr was set.

The adhesion between the film of the optical disk thus prepared and the substrate was examined by a scratch test method and a pull test method. As a comparative example, a disk constructed of three layers using only the sputtering method without using the ion mixing method was used. the result.

A disc made without using the present invention weighs 0.6 kg/
Peeling occurred between the substrate and the film under the tensile load of d. On the other hand, the disc manufactured according to the present invention has 6
．． It peeled off only when a tensile load of 3 kg/aJ was applied. Thus, by using the present invention, it was possible to significantly improve adhesiveness. Furthermore, when this optical disc was left in a high temperature and high humidity environment of 60°C and 95% RH, discs that did not use the present invention began to peel after being left for 160 hours, and peeling was observed on almost the entire surface of the disc after 200 hours. Ta. On the other hand, the disk produced according to the present invention has a temperature of 60°C - 95°C for 1000 hours.
The metal nitrogen material thus formed, which does not generate any peeling cracks even when left in a %RH environment, serves as a protective layer that prevents water and oxygen from diffusing into the information recording film.

In addition, Ksrr measured through the substrate of the magneto-optical recording film
The rotation angle remained constant at 0.30@ and did not change at all before and after being left at 60° C. and 95% RH for 1000 hours. On the other hand, in the case of the disk manufactured by the normal sputtering method 1, the err rotation angle gradually began to decrease after 250 hours, and after 1000 hours, the value decreased by about 40% to 0.191. As described above, the mixed layer of the substrate material and the film material has the property of protecting against moisture and oxygen, and the present invention is effective from the viewpoint of the life span of the disk.

In addition, although the EB evaporation method is used to form a film on the substrate, ordinary sputtering methods such as sputtering method, resistance heating evaporation method, and ion blating method can also be used.
This does not in any way hinder the effects of the present invention.

[Example 2] In this example, film formation was performed after activating the substrate surface with plasma. A schematic diagram of the cross-sectional structure of the optical disc prepared is shown in Fig. 3. . The optical disc was manufactured according to the procedure described below.

First, a substrate having a resin surface or a surface of a resin substrate was subjected to treatment 7 with inert gas plasma. The processing methods include 1) reverse sputtering using a normal sputtering device, 2) reactive ion etching, and 3
) There is a first method using ion milling, but the same effect can be obtained by using either method. The most suitable inert gas to be used is A r * N z t He, among others, He is most suitable for treating the surface of a substrate with low heat resistance or a thermoplastic substrate. This is because the surface processing speed with He is slow and at the same time the substrate surface Φ cooling effect is large. In addition, a reactive gas such as 02 or H2 may be used instead of an inert gas.6 Surface treatment with a reactive gas modifies the substrate surface and increases the number of active points that contribute to bonding. When the film is formed on the substrate, a strong bond is formed between the film material and the substrate surface. As a result, the adhesive strength between the film and the substrate increased. This was confirmed by following the change in the absorption peak of the infrared absorption spectrum.

After performing the surface treatment in this manner, silicon nitride as the base film 8 was formed by sputtering under the following conditions. 51g Na sintered body as target, A as discharge gas
r were used respectively. The sputtering conditions were: input RF power density: 4.5W/cd, discharge voltage: I x 10
A silicon nitride base film 8 having a film thickness of 850 mm and a refractive index n = 2.05 was formed at a substrate rotation speed of 2 Orpm.Subsequently, as an information recording medium film 9, Tbz
a, oFeel, oCotz, oNba, a amorphous film 9
was formed by sputtering method. An alloy having the above composition was used for the target, and pure Ar was used for the discharge gas. The sputtering conditions are input RF power density: 4
．． 5W/ad, discharge gas pressure crab 5 X 10-8 (To
rr), and the substrate rotation speed is 2 Orpm.

Finally, a silicon nitride protective film 10 was formed by sputtering. The manufacturing method is to set the discharge gas pressure to 2
It is the same as the case of the base film 8 except that it is set to 10-'' (Torr).

The adhesion of the optical disk thus prepared was examined by leaving the disk in a high temperature, high humidity environment (60 DEG C.-95% RH) and examining the occurrence of peeling. A comparison was made with a disk in which a base film, a recording film, and a protective film were directly formed without performing plasma irradiation treatment. As a result, disks manufactured without using the manufacturing method of the present invention were tested at 60℃-95℃.
%RH, peeling occurred between the substrate and the underlying film after 160 hours. On the other hand, in the case of a disc manufactured using the method of the present invention, 1000 hours and 60 hours
Although the film was left at 95% RH, no peeling occurred. Further evaluation tests are currently underway. Yuko's method, which found that plasma irradiation has the effect of increasing the adhesive strength between the substrate and the film formed on it, shows that it can be used not only on the substrate surface but also when forming a laminated film. Plasma treatment of the surface before forming each layer has the effect of increasing adhesive strength. The effect of this plasma treatment is not only to increase the adhesive strength, but also to greatly improve the squareness of the Kerr hysteresis obtained when the magneto-optical pattern 9a film is formed as an information recording film, contributing to an increase in the Kerr rotation angle. I discovered that. FIG. 4 shows the change in Karr hysteresis at that time. Both have Tb-rich composition (
First, the err hysteresis curve of the disk fabricated using the present invention is 11
As shown in the figure, it has good squareness. On the other hand, the err hysteresis of the disk manufactured without using the present invention is as shown by curve 12 in the same figure, as the squareness deteriorates, the coercive force HC increases, and conversely, the Kerr rotation angle θ Diminished. This difference in the hysteresis curves is due to the fact that floating oxygen on the substrate surface was removed by the plasma irradiation, which greatly suppressed the formation of an oxide layer at the interface of the substrate or base film. In this regard, secondary ion mass spectrometry (
When the depth profile was examined by SIMS, it was confirmed that the oxygen peak that existed near the substrate surface disappeared due to plasma irradiation.

[Example 3] This example is a case where only one layer of magneto-optical recording film is formed on a disk substrate. The apparatus used for producing the magneto-optical disk was the same as in Example 1, as shown in FIG. Fire N2 from the ion source.

The alloys of TbFeCo (source I) and NbPt (source ■) are used as evaporation sources and are evaporated by EB.

First, a resin substrate is used, and after the substrate surface is irradiated with a neutral nitrogen beam to modify the substrate surface, source I and source ■ are evaporated from an EB evaporation source, and a nitrogen beam is also irradiated at the same time. 14 mixed layers of 100 substrates and recording film materials were formed.

After that, the nitrogen beam irradiation was stopped and the TbFeCoNbP
The T film 15 was formed for 800 people, and finally the nitrogen beam and two sources were simultaneously deposited to form the film 16 for 300 people. At that time, the amount of evaporation of sauce (■) was made larger than that of sauce (I). The magnetic properties of the film thus formed are as follows: Curie temperature: 210°C, compensation temperature: 60°C, Kerr rotation angle: 0.
33. The coercive force was 10 K Oe, and when the C/N of this disk was evaluated, it was 50 dB.
(2MHz.

N = 0.5), and there was almost no difference between this and that of a magneto-optical disk formed by a normal sputtering method.

Next, changes in film adhesion and various properties of the disk were examined when this disk was stored at 60° C. and 95% RH. As a result, 1. Even when the disk produced using the present invention was left in this environment for more than 1000 hours, no peeling was observed, and the C/N did not decrease. On the other hand, the magneto-optical disk produced without using the present invention had 3
After 00 hours, peeling and cracking began to occur.

Therefore, the measurement of C/N was a matter of national importance. As described above, the present invention was extremely effective in improving adhesiveness.

[Example 4] This example is a case where a plasma-enhanced chemical phase deposition (CVD) method or a laser-enhanced CVD method is used as a manufacturing method for a magneto-optical recording medium formed on a disk substrate. FIG. 6 shows a diagram of the principle of the apparatus used to create the disc. This figure shows an example of a plasma-excited CVD device, but the laser-excited CVD
In the case of VD, the principle and reaction mechanism are the same except for the excitation source.The device consists of an outer reaction tube 17 and an inner tube 22.
It consists of double reaction tubes. Outer reaction tube 17
An RF coil 18 that generates plasma is installed around the . The lower end of the coil 18 was made flush with the magneto-optical disk substrate 19.

Then, when plasma is generated, the substrate 19 is exposed to the plasma 20 as shown in 20, and at the same time a film is deposited, a part of the deposited part is sputtered, as if sputtering is being done while milling. . Further, the substrate 19 was externally controlled by a heater or cooling jig 21 according to temperature changes so that the temperature was always 80°C.

The raw material gas flows down from the top of the reaction tube. Metal alcoholade was used as a sauce source. Using this device, the atmosphere is controlled, Nz is appropriately mixed into the carrier gas, and the substrate/
TbFeCoNbPtN/TbFeCoNbPt
A magneto-optical disk having a structure of /TbFaCoNbPtN was formed. Here, as the substrate, a plastic substrate or a substrate whose surface on which a film is formed is made of resin was used. When the substrate was placed in the position shown in FIG. 6, the deposition rate of the film decreased to about 1/2 of normal CVD, but the bulk density of the film increased to 88% (normally 70%).

A lifespan test was conducted on the disc thus prepared. The disks were left in a high temperature, high humidity environment of 60° C. and 5% RH, and the occurrence of cracks and peeling of the film, as well as the deterioration of the recording film, were investigated. As a comparative example, a disk having a medium configuration similar to that of this example was used. As a result, cracks appeared on the entire surface of the disk of the comparative example after being left in this environment for only 50 hours. On the other hand, in the disk formed according to the present invention, even after being left for 1000 hours, not only did the film not peel off or crack, but the magnetic properties did not change at all. As described above, by simultaneously performing plasma irradiation and film formation according to the fourth aspect of the present invention, the substrate surface can be activated and film formation can be performed at the same time, thereby increasing the affinity between the substrate and the film, resulting in improved adhesion. This result is observed not only when forming a magneto-optical recording film but also when any type of thin film is formed.

〔Effect of the invention〕

According to the present invention, by activating or modifying the surface of a plastic substrate or a resin surface of a substrate whose surface layer is made of resin using a method such as a plasma irradiation method or an ion mixing method, the substrate and its surface can be activated or modified. This has the effect of improving adhesion with the film formed on the surface. In addition, when the present invention is used,
When surface impurity layers are removed by surface modification techniques and an inorganic dielectric or magneto-optical recording film is formed, the influence of these impurity layers can be removed, resulting in stable optical or magnetic properties. Furthermore, the effect of extending the life of the disk by approximately 1.8 times was observed by removing these.

[Brief explanation of the drawing]

1, 3, and 5 are schematic diagrams of the cross-sectional structure of a magneto-optical disk according to an embodiment of the present invention, FIG. 2 is a diagram showing an ion mixing device, and FIG. 4 shows that plasma irradiation has a Kerr hysteresis shape. FIG. 6 is a schematic diagram showing the principle of a plasma CVD apparatus. 1.6, 13.19... Substrate, 2.14... Mixture layer, 3.8... Base film, 4, 9... Information recording film, 5
, 10... Protective film, 7... Plasma active part, 15...
... Magneto-optical recording material, 16... Nitrogen-containing layer, 17...
・Reaction tube, 18...RF coil, 20...Plasma, 21...Cooling jig, No. 1I! 1 2nd (! 1 3rd mouth 4th concave

Claims (1)

[Claims] 1. A method for manufacturing an optical disc in which recording, reproduction, and erasing is performed using laser light, characterized in that the surface of the disc substrate is modified to lower the surface energy before forming the optical recording medium. A method of manufacturing an optical disc. 2. A method for manufacturing an optical disc, characterized in that the substrate according to claim 1 is a substrate whose surface is a resin layer or a substrate whose entire surface is made of resin. 3. Manufacture of an optical disk characterized in that the surface modification method according to claim 1 uses a method of irradiating plasma of an inert gas that does not react with the substrate material or an inert gas containing a reactive gas. Method. 4. A method for manufacturing an optical disk, characterized in that an ion implantation or ion mixing method is used as the surface modification method according to claim 1. 5. An optical disc characterized in that a mixture layer of a substrate material and a lowermost layer material of the optical recording medium is present between the substrate and the lowermost layer of the optical recording medium by the surface modification method described in claim 1. manufacturing method. 6. As the inert gas according to claim 3, A
A method for manufacturing an optical disc, characterized in that at least one element selected from r, He, and N_2 is used. 7. As the reactive gas described in claim 3, O
_2, H_2, and a mixed gas based on at least one element selected from Ar, He, and N_2 inert gases. Production method.